1. Field of the Invention
The present invention is directed to a method for efficiently and economically removing dissolved hydrogen sulfide frequently found in potable water. The method involves first chlorinating the water with chlorine to convert about 90% of the hydrogen sulfide to sulfates, and then passing the chlorinated water through a bed of activated carbon whereby the remaining about 10% hydrogen sulfide will be catalytically converted into elemental sulfur.
2. Background of the Invention
Hydrogen sulfide is formed in water bodies by the decomposition of organic material under anaerobic conditions. The resulting hydrogen sulfide imparts the familiar odor of rotten eggs to the water and a "sulfur-like" taste. While many people drink "sulfur water" because it is the only water available, it is not generally regarded as acceptable to the public. In addition, it has been determined that the reaction of sulfide and normal water plant chlorine dosages causes an even more intense taste and odor problem in the potable water distribution system.
The most common method available today for sulfide removal is aeration of the raw water by one of several available techniques. However, aeration of "sulfur water" involves numerous inherent problems. Perhaps most important, aeration at best is only 50-60% efficient, thereby allowing untreated sulfides to enter the storage reservoir or distribution system. Additionally, as a necessary adjunct to the aeration process, hydrogen sulfide gas is released into the surrounding atmosphere causing a pollution problem and, possibly, problems relating to toxicity. Finally, hydrogen sulfide that is not removed in the aeration process enters the storage and distribution system resulting in rapid growth of sulfide-reducing bacteria comprised mainly of Beggiatoa Albans. Not only are these growths aesthetically unacceptable, but also they result in clogging of storage and distribution systems.
While it is well known in the field of water treatment to utilize procedures and apparatus for chlorinating potable water and also for filtering the water prior to storage and distribution, virtually no teachings are available concerning such a process for the effective removal of hydrogen sulfide. In fact, as stated above, modern chlorination and aeration treatment actually aggravates the odor and taste problems associated with "sulfur water." Furthermore, such modern treatment processes are directed to sterilizing the water or removing organic contaminants therefrom. For example, U.S. Pat. No. 3,733,266 discloses a process for oxidizing ammonia in municipal wastewater using breakpoint chlorination followed by passing the treated wastewater across a carbon adsorption zone. U.S. Pat. No. 3,252,899, teaches the use of an activated carbon filter in a process for removing organic contaminants from water. U.S. Pat. No. 1,771,518, also teaches the use of chlorine and a carbon bed filter in a process for disinfecting water. Additional examples of the current state of the art with regard to both processes and filtration devices and techniques are shown in the following U.S. Letters Patent:
______________________________________ 2,238,896 Gibbons 2,605,901 Morrison, et al 2,633,990 Simpson, et al 3,337,454 Gruenwald 3,835,038 Heaney 3,915,857 Olson 3,928,197 Horan, et al 3,932,278 Meidl, et al Re. 27,275 Dajani ______________________________________
However, none of the above teachings are specifically concerned with the unique problems set forth above with regard to the removal of dissolved hydrogen sulfide from potable water.
With the advent of a public consciousness concerning environmental pollution as well as the quality of our drinking water, aeration is no longer a desirable method for hydrogen sulfide removal. It is therefore clear that there is a great need in the art for a method which would eliminate the hydrogen sulfide without exposing the water to the ambient atmosphere. Such a process should be simple in design, operation and cost-effectiveness while requiring minimal operating tolerances. Of course, in order to be truly effective the process should remove substantially 100% of the dissolved hydrogen sulfide content.